WHITE RIVER JUNCTION — The man accused of torching three school buses a year ago had a history of playing with fire and threatening to burn things down, witnesses told police.

Robert Duprey, 26, of White River Junction was held for lack of $50,000 bail Monday after he pleaded innocent to felony charges of third-degree arson and unlawful mischief.

The Aug. 26, 2012, fire caused $200,000 in damage as it spread between the tightly parked buses in downtown White River Junction, police said.

A year ago Duprey was living in The Haven homeless shelter just up the hill from Pine Street and the Butler Bus Service maintenance building where the fire occurred. He would walk to West Lebanon, N.H., to his job in the mailroom of the Valley News newspaper.

Police said a co-worker there told investigators, “Robert is known for threatening to burn things” and “he would get mad and threaten to burn the Valley News to the ground.”

Hartford Police Detective Christopher Aher, who responded to the fire, said the only person in the area was Duprey watching the flames from a nearby parking lot.

Another witness to the fire told police Duprey had flagged her down as she was driving past and asked her to use her cellphone to call the fire department.

Aher said Duprey told him he'd been walking home from work when he “heard coughing,” saw a spark or glow inside a bus, and then heard someone run away. Duprey admitted to having a lighter with him that night but denied any involvement, the detective said.

Duprey was subsequently arrested in a string of more than a dozen late-night burglaries into cars. But police said the arson case lay largely dormant until May, when other witnesses, including Duprey's ex-girlfriend, said Duprey had told them he'd started the bus blaze.

Aher said the ex-girlfriend, Ashley Richarson, 21, described Duprey as taking drugs and playing with lighters and constantly starting small fires during their relationship.

The detective said Duprey volunteered to take a polygraph test, but failed to show up. Duprey claimed it was because he had to work that afternoon, said Aher, adding that Duprey's employer denied it.